1. Field of Invention
The present invention relates generally to the field of wireless communication and data networks. More particularly, in one exemplary aspect, the present invention is directed to enhanced methods and apparatus for wireless femtocell setup and self-coordination.
2. Description of Related Technology
Universal Mobile Telecommunications System (UMTS) is an exemplary implementation of a “third-generation” or “3G” cellular telephone technology. The UMTS standard is specified by a collaborative body referred to as the 3rd Generation Partnership Project (3GPP). The 3GPP has adopted UMTS as a 3G cellular radio system targeted for inter alia European markets, in response to requirements set forth by the International Telecommunications Union (ITU). The ITU standardizes and regulates international radio and telecommunications. Enhancements to UMTS will support future evolution to fourth generation (4G) technology.
A current topic of interest is the further development of UMTS towards a mobile radio communication system optimized for packet data transmission through improved system capacity and spectral efficiency. In the context of 3GPP, the activities in this regard are summarized under the general term “LTE” (for Long Term Evolution). The aim is, among others, to increase the maximum net transmission rate significantly in the future, namely to speeds on the order of 300 Mbps in the downlink transmission direction and 75 Mbps in the uplink transmission direction.
In the incipient version of the LTE specification (Release 8), the 3GPP standards body will formalize requirements for a network element referred to as the “Home enhanced-NodeB” (HeNB). The Home eNodeB (HeNB) will be deployed for LTE based Radio Access Technology (RAT) networks; the HeNB is an evolution of the Home NodeB (HNB), which is its UMTS RAT predecessor. Both HeNBs and HNBs are femtocells that are optimized for use in residential, corporate, or similar environments (e.g., private homes, public restaurants, small offices, enterprises, hospitals, etc., and hence the term “home” of “Home NodeB” is not meant to be limiting to residential applications). In the present context, the terms “Home Base Station”, “Home NodeB” (for UMTS), “Home eNodeB” (for LTE), and “femtocell” refer to the same logical entity, and are used interchangeably unless otherwise specifically noted.
Femtocell Operation—
Generally speaking, a femtocell is a base station designed specifically for areas of limited coverage, to service a small number of users (e.g., small business and home environments). A femtocell augments the service provider's existing network of base stations by connecting to the service provider's network via a broadband interface (such as DSL, FiOS, T1, ISDN, or DOCSIS cable modem). Due to the smaller size and lower cost of a femtocell, they can be utilized in areas which are otherwise not feasibly serviced through standard base station deployments (e.g., by extension of indoor service coverage, or temporary service coverage). They also may be portable in nature, and accordingly be repositioned when desired with fairly minimal effort. Various aspects of femtocells are described in greater detail subsequently herein.
The random nature of femtocell deployments creates some unique challenges for network operators. Prior to the deployment of femtocells, base station networks were planned and controlled entirely by the network operator. Physical spectrum was easily controlled by a network operator with fixed base station allocations. In contrast to regular fixed base stations, femtocells are not planned, and in fact may widely vary in usage. Multiple femtocells may be operated simultaneously in a crowded area (such as in an apartment complex) or in relative isolation (e.g., on a farm, etc.). Furthermore, the number of terminal devices supported by each femtocell is widely unpredictable, ranging from a single user (personal use), to many users (e.g., for an enterprise application such as a coffee house or larger business).
Existing methods for spectrum allocation require frequent communications between the femtocell and network operator to allocate/free radio resources. Reducing interference between a femtocell and its neighboring cells requires radio resource setup and management and interference coordination. However, centralized coordination of femtocells results in a significant processing burden on the network operator, including signaling its femtocell interfaces (e.g., due to transmission of power control commands between the network operator and the femtocell). In a large-scale deployment scenario of HeNBs in an LTE network, hundreds (or more) of HeNBs may be deployed within the coverage of a macrocell, with all HeNBs sharing the same licensed spectrum.
The network operator is figuratively pulled in multiple directions: too much supervision is costly in both processing power and network overhead, whereas too little supervision leads to inefficient usage of spectral resources (and perhaps even more dire resource-related consequences such as service delays or outages).
Accordingly, improved methods and apparatus are needed to efficiently manage spectrum allocation for random dispersions of femtocells. Such improved methods and apparatus should provide relatively efficient usage of spectral resources. Ideally, femtocells implementing these methods and apparatus may obtain, use and release spectral resources in a timely fashion; allocated resources which are unused are in effect wasted, which reduces inter alia cost efficiency and profit for the network operator.
Lastly, the improved methods and apparatus should preferably minimize dialogue between the femtocell and the Core Network. Efficient network inter-device communication greatly reduces the Core Network's processing burden for supporting widespread femtocell deployments.